linux-kernel - Re: [PATCH v24 09/34] ASoC: Add SOC USB APIs for adding an USB backend

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Message-ID: <09fde4e6-c3be-484d-a7a5-bd653dc42094@linux.intel.com>
Date: Thu, 1 Aug 2024 10:02:12 +0200
From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To: Wesley Cheng <quic_wcheng@...cinc.com>, srinivas.kandagatla@...aro.org,
 mathias.nyman@...el.com, perex@...ex.cz, conor+dt@...nel.org,
 corbet@....net, broonie@...nel.org, lgirdwood@...il.com, krzk+dt@...nel.org,
 Thinh.Nguyen@...opsys.com, bgoswami@...cinc.com, tiwai@...e.com,
 gregkh@...uxfoundation.org, robh@...nel.org
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-sound@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-doc@...r.kernel.org,
 alsa-devel@...a-project.org
Subject: Re: [PATCH v24 09/34] ASoC: Add SOC USB APIs for adding an USB
 backend




> +/**
> + * struct snd_soc_usb_device
> + * @card_idx - sound card index associated with USB device
> + * @pcm_idx - PCM device index associated with USB device
> + * @chip_idx - USB sound chip array index
> + * @num_playback - number of playback streams
> + * @num_capture - number of capture streams

so here we have a clear separation between playback and capture...

> + * @list - list head for SoC USB devices
> + **/
> +struct snd_soc_usb_device {
> +	int card_idx;
> +	int pcm_idx;
> +	int chip_idx;
> +	int num_playback;
> +	int num_capture;
> +	struct list_head list;
> +};
> +
> +/**
> + * struct snd_soc_usb
> + * @list - list head for SND SOC struct list
> + * @component - reference to ASoC component
> + * @num_supported_streams - number of supported concurrent sessions

... but here we don't. And it's not clear what the working 'sessions'
means in the comment.

> + * @connection_status_cb - callback to notify connection events
> + * @priv_data - driver data
> + **/
> +struct snd_soc_usb {
> +	struct list_head list;
> +	struct snd_soc_component *component;
> +	unsigned int num_supported_streams;
> +	int (*connection_status_cb)(struct snd_soc_usb *usb,
> +			struct snd_soc_usb_device *sdev, bool connected);
> +	void *priv_data;
> +};

> +/**
> + * snd_soc_usb_allocate_port() - allocate a SOC USB device

USB port?

> + * @component: USB DPCM backend DAI component
> + * @num_streams: number of offloading sessions supported

same comment, is this direction-specific or not?

> + * @data: private data
> + *
> + * Allocate and initialize a SOC USB device.  This will populate parameters that
> + * are used in subsequent sequences.
> + *
> + */
> +struct snd_soc_usb *snd_soc_usb_allocate_port(struct snd_soc_component *component,
> +					      int num_streams, void *data)
> +{
> +	struct snd_soc_usb *usb;
> +
> +	usb = kzalloc(sizeof(*usb), GFP_KERNEL);
> +	if (!usb)
> +		return ERR_PTR(-ENOMEM);
> +
> +	usb->component = component;
> +	usb->priv_data = data;
> +	usb->num_supported_streams = num_streams;
> +
> +	return usb;
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_allocate_port);
> +
> +/**
> + * snd_soc_usb_free_port() - free a SOC USB device
> + * @usb: allocated SOC USB device
> +
> + * Free and remove the SOC USB device from the available list of devices.

Now I am lost again on the device:port relationship. I am sure you've
explained this before but I forget things and the code isn't
self-explanatory.


> + *
> + */
> +void snd_soc_usb_free_port(struct snd_soc_usb *usb)
> +{
> +	snd_soc_usb_remove_port(usb);
> +	kfree(usb);
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_free_port);
> +
> +/**
> + * snd_soc_usb_add_port() - Add a USB backend port
> + * @usb: soc usb device to add
> + *
> + * Register a USB backend device to the SND USB SOC framework.  Memory is
> + * allocated as part of the USB backend device.
> + *
> + */
> +void snd_soc_usb_add_port(struct snd_soc_usb *usb)
> +{
> +	mutex_lock(&ctx_mutex);
> +	list_add_tail(&usb->list, &usb_ctx_list);
> +	mutex_unlock(&ctx_mutex);
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);
> +
> +/**
> + * snd_soc_usb_remove_port() - Remove a USB backend port
> + * @usb: soc usb device to remove
> + *
> + * Remove a USB backend device from USB SND SOC.  Memory is freed when USB
> + * backend is removed.
> + *
> + */
> +void snd_soc_usb_remove_port(struct snd_soc_usb *usb)
> +{
> +	struct snd_soc_usb *ctx, *tmp;
> +
> +	mutex_lock(&ctx_mutex);
> +	list_for_each_entry_safe(ctx, tmp, &usb_ctx_list, list) {
> +		if (ctx == usb) {
> +			list_del(&ctx->list);
> +			break;
> +		}
> +	}
> +	mutex_unlock(&ctx_mutex);
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);